A126510 Number of base 15 n-digit numbers with adjacent digits differing by four or less.

1, 15, 115, 915, 7355, 59369, 479887, 3880945, 31391483, 253929457, 2054110259, 16616430593, 134416594859, 1087347726489, 8795978441155, 71154097145873, 575593242083915, 4656198285106057, 37665804590772499, 304693389569808737

Offset

0,2

Comments

[Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4.

Links

Table of n, a(n) for n=0..19.

Formula

G.f.: (1+6*x-18*x^2-48*x^3-6*x^4+24*x^5+8*x^6) / (1-9*x+2*x^2+42*x^3+14*x^4-20*x^5-8*x^6) (conjectured). - Colin Barker, Jul 18 2017

Prog

(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))

Crossrefs

Cf. Base 15 differing by three or less A126483, two or less A126402, one or less A126369.

Sequence in context: A044728 A091347 A125352 * A328725 A331211 A183475

Adjacent sequences: A126507 A126508 A126509 * A126511 A126512 A126513

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved